1. Field of the Invention
The present invention relates to a drained, face seal for sealing, from the ambient, a pressurized fluid in the interior or a housing fitted with a rotatable shaft and for eliminating fluid leakage along the shaft.
2. Description of the Prior Art
The majority of seals used on rotating shafts in pressurized environments are contact seals which include a rotor fixed to the shaft and a stator fixed to the housing. In these traditional seals, when the shaft rotates the rotor and the stator physically contact and slide relative to one another. As a result, abrasion occurs between the faces of the rotor and the stator. Such contact seals, therefore, typically require lubrication on or between the rubbing faces of the rotor and stator, particularly when subjected to high pressures and excessive speeds. The lubrication between the sealing faces can and does leak toward the ambient, often onto the rotating shaft and associated bearings.
Since contact seals exhibit undesirable wear characteristics in certain circumstances, efforts have been made to produce non-contact seals having a gap formed between the rotor and the stator to thereby eliminate rubbing. Non-contact seals also present the problem of leakage of fluid between the sealing faces of the rotor and stator and onto the shaft. Conventional non-contact seals tend to leak along the shaft to a degree depending on the size of the gap maintained between the seal faces.
Some efforts to provide drainage have been made in connection with contact seals. Examples of contact seals attempting to control leakage are described in U.S. Pat. No. 4,406,459 to Davis et al. entitled Oil Weepage For Carbon Seal Plates and U.S. Pat. No. 4,529,209 to Nii et al. entitled Machine Shaft Seal with Centrifugal Removal Of Sand and Particles. These contact seals are designed, respectively, to pump out fluid into the high pressure side of the rotor and to drain water from sand particles upon the opening of a valve. Another example is U.S. Pat. No. 4,523,764 to Albers et al. entitled Fluid-Sealed Shaft Seal With Bores For Supplying and Discharging Fluid. The disclosed externally activated seal in Albers et al. has a stator which includes at least one sealing fluid supply bore and at least one fluid discharge bore for supplying and discharging buffer sealing fluid to and from the gap, to maintain a gap width. Fluid is pumped through these bores. The seal also includes spiral grooves for supplying the auxiliary sealing fluid to establish an annular zone of elevated pressure for preventing escape of the sealing fluid.
Conventional non-contact face seals have additional limitations, since they have generally utilized spiral type grooves in the face of the rotor. Examples of such seals are described in U.S. Pat. No. 4,212,475 to Sedy entitled Self Aligning Spiral Groove Face Seal. These non-contact seals are designed to function in a unidirectional manner. If the seals are driven in the opposite direction, they will not separate but will be pulled or sucked toward each other, thereby increasing wear and ultimately destroying the seal. For these and other reasons, the non-contact seals employing spiral grooves have significant limitations.